> Others include permissions and storage space issues with your queue
> directory and various other configuration errors. What is sent back to the
> client in this class of circumstances is documented as being "intentionally
> vague" so you really do need to look at the log for useful info.

Right, a transient error storing the data into the queue, that is not
message too large (so missing ESMTP SIZE is probably not it...)

Anyway the OP's original post clearly included text that advised him to
read his logs for more details. There would have been no need to guess
at the cause had this advice not been ignored.

--
Viktor.
P.S. Morgan Stanley is looking for a New York City based, Senior Unix
system/email administrator to architect and sustain our perimeter email
environment. If you are interested, please drop me a note.